FHDS Signal Interference Resistance in M2M Networks
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Solution Overview
Problem
Existing wireless communication technologies for machine-to-machine (M2M) networks face challenges in maintaining reliable and secure communication in noisy, crowded environments with varying physical conditions and interference from other devices.
Innovation Solution
The method employs a frequency-hop direct-sequence (FHDS) spread-spectrum modulation format within the 902-928 MHz ISM band, using cyclic chip-level and symbol-level cyclic prefixes to control channel multipath and interference. This method randomly determines transmission information at each node, including physical dwell, spreading code, and source symbol mask, which is not known to receivers or provisioned by the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spread-spectrum modulation with random transmission information is used, then security and interference resistance are improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic frequency hopping where transmission frequency changes according to a pseudorandom sequence known to both transmitter and receiver. This dynamic approach allows the system to adapt to interference conditions while maintaining manageable complexity through pre-synchronized hopping patterns rather than fully random selection
Solution Approach 2:
The system changes multiple transmission parameters simultaneously including frequency offset, spreading code, and modulation scheme according to pseudorandom sequences. These parameter variations enhance security and interference resistance while the receiver can track changes using synchronized pseudorandom generation, balancing complexity with performance
2Reliability
If cyclic prefixes are added to control multipath, then reliability is improved, but loss of time increases
Solution Approach 1:
The patent uses cyclic prefixes of optimized length that provide sufficient multipath protection for typical channel conditions without excessive overhead. The prefix length is carefully chosen to cover the expected delay spread while minimizing time loss, representing a balance between protection and efficiency rather than maximum possible protection
3Reliability
If random transmission information is used at each node, then security is improved, but ease of operation worsens
Solution Approach 1:
Each node in the network autonomously generates its own pseudorandom transmission parameters using locally stored seed values or algorithms. This self-service approach eliminates the need for centralized provisioning of random parameters, maintaining high security while simplifying network operation and configuration
Solution Approach 2:
The system incorporates synchronization mechanisms where nodes exchange timing and frequency reference information to maintain coherent pseudorandom sequences. This feedback ensures that random parameter selection does not prevent successful communication, balancing security with operational ease
Data Source
AI summary
In a shared-medium network, a hopping pattern provisioned by a transmitting device designates a plurality of frequency channels and a corresponding plurality of times. The transmitting device splits data into multiple radio-burst payloads, and transmits the data on the frequency channels according to the hopping pattern, wherein an intended receiving device has no prior knowledge of the hopping pattern. The resulting unpredictable transmission property provides robust, efficient, and interference-resistant reception in the presence of networks operating with different standards and disparate organization. Additional aspects allow reception of ad-hoc transmissions in dense environments without scheduling, CSMA/CA protocols, or scheduling feedback paths; and allows macro-diverse reception of transmissions at networks of connected receivers, thereby providing additional efficiency and security improvements that exploit route diversity of the network.